1. Field of the Invention
The present invention relates to a keyboard apparatus in which an arm is driven by a key to move to thereby apply an inertial force to the key when the key is depressed.
2. Description of the Related Art
Conventionally, a keyboard apparatus is known in which arms having mass are provided such that each of the arms moves e.g. pivotally in accordance with depression of the associated key so as to improve key touch feeling.
For example, a keyboard apparatus disclosed in Japanese Laid-Open Utility Model Publication (Kokai) No. H02-64992 is configured such that an arm provided with a weight is pivotally disposed on a slide member which slides in accordance with key depression, so as to transmit displacement of the associated key which is depressed to the slide member. When the key is depressed, in the first half of the key depression stroke, the associated arm is driven by the key, for pivotal motion, but halfway in the key depression stroke, the key is disengaged from the arm by a sliding motion of the slide member, and the pivotal motion of the arm is stopped. Consequently, from then on, the load of the arm is not applied to the key.
Further, a keyboard apparatus disclosed in Japanese Patent No. 3221283 is configured such that a driving part of a key and a driven part of the associated pivotally movable arm (mass body) are constantly held in engagement with each other, and in a key depression stroke, an inertial force of the arm is imparted to the key via the driving part and the driven part.
Furthermore, conventionally, keyboard apparatuses have been proposed in which touch feeling (hereinafter referred to as “key touch feeling”) can be changed. For example, in a keyboard apparatus proposed in Japanese Patent Publication (Kokoku) No. H01-47798, an arm having one end thereof engaged with a key and the other end thereof provided with a weight is configured such that the arm can be driven by the key via the one end in accordance with key depression, for pivotal motion about a support member. Further, the position of the other end of the arm can be adjusted within a range between an upper limit position and a lower limit position. When the position of the other end is set to the lower limit position, the arm is allowed to pivotally move about the support member in accordance with key depression, but when the position of the other end is set to the upper limit position, the other end cannot come into contact with the support member, so that no pivotal motion of the arm about the support member occurs. Thus, the weight of key touch feeling can be changed according to a position set for the other end of the arm.
In general, from the viewpoint of realizing expressive performance by a keyboard apparatus, it is considered desirable that an inertial force acts relatively lightly during strong key depression, i.e. when a key is quickly depressed, and acts relatively heavily during weak key depression, i.e. when a key is slowly depressed. However, in Japanese Laid-Open Utility Model Publication (Kokai) No. H02-64992, the key is always disengaged from the arm at a predetermined position in the key depression stroke, so that the same load is applied to the key in the same range of the key stroke irrespective of the intensity of the key depression. Further, in Japanese Patent No. 3221283, since the driving part of the key and the driven part of the arm are constantly held in engagement with each other, the same load is applied to the key in the same range of the key stroke irrespective of the intensity of key depression.
Therefore, these conventional keyboard apparatuses leave room for improvement in enhancement of key touch feeling in consideration of key depression intensity.
In Japanese Patent Publication (Kokoku) No. H01-47798, one end of the arm is constantly held in contact with the associated key, and besides, the arm also has mass in other parts than the weight. For this reason, even when the other end of the arm is at the upper limit position and the arm is kept from contact with the support member, the arm moves along with the key, and hence not a little inertial force generated by the motion of the arm is constantly applied to the key. Therefore, there is a limit to a setting for making key touch feeling light, and there still remains room for further improvement in changing key touch feeling distinctly and over a wide range.